Clutch spring

ABSTRACT

A clutch spring for use in calibration assembly including a sleeve-like body having first and second longitudinal edges spaced from each other and a leg extending from one of the longitudinal edges to form a stop. The calibration assembly includes the above described clutch spring gripping a cylindrical clutch surface of a rotatable adjustment member which is adapted to engage a thermostat of the type operating a control device in response to temperature variations and a temperature adjusting device controlling the position of the adjustment member.

United States Patent [191 Freeby 11] 3,794,312 Feb. 26, 1974 1 CLUTCHSPRING [75] Inventor: Leroy W. Freeby, Long Beach,

Calif.

[73] Assignee: Robertshaw Controls Company,

Richmond, Va.

[22] Filed: June 9, 1972 211 Appl. No.: 261,349-

Related U.S. Application Data [62] Division of Ser. No. 35,698, May 8,1970.

[52] U.S. Cl. 267/156 [51] Int. Cl Fl6f H06 [58] Field of Search...267/156, 164, 165, 134, 135,

[56] References Cited UNITED STATES PATENTS 3,003,773 10/1961 Fuehrer267/164 3,551,921 1/1971 Fox et a1 267/164 Primary Examiner.lames B.Marbert Attorney, Agent, or Firm Anthony A. OBrien 57 ABSTRACT A clutchspring for use in calibration assembly including a sleeve-like bodyhaving first and second longitudinal edges spaced from each other and aleg extending from one of the longitudinal edges to form a stop.

The calibration assembly includes the above described clutch springgripping a cylindrical clutch surface of a rotatable adjustment memberwhich is adapted to engage a thermostat of the type operating a controldevice in response to temperature variations and a temperature adjustingdevice controlling the position of the adjustment member.

9 Claims, 6 Drawing Figures CLUTCH SPRING CROSS REFERENCE TO RELATEDAPPLICATIONS The present application is a division of my copendingapplication, Ser. No. 35,698 filed May 8, 1970.

BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention pertains to clutch springs and, more particularly, tothermostat calibration assemblies utilizing such clutch springs.

2. Description of the Prior Art Thermostatically operated'controldevices, such as water heater thermostats and space thermostats, arenormally calibrated in the environment in which they are to be used.That is, calibration is performed after installation in order that anyadverse effects therefrom may be obviated. In the past such devices havebeen provided with relatively complex calibration assemblies, andcalibration procedures have been more complex than is desirable. 1

More specifically, for water heater applications rod and tubethermostats are normally utilized to control a valve means in accordancewith temperature variations of water in the water heater tank. Therodnormally operates at an intermediate position on a lever which has anoperating end controlling the valve means through a snap actingactuation mechanism and a fulcrum end which is positioned in accordancewith the desired water temperature to be maintained by the water heater.The fulcrum end normally receives an extension rod which is mounted in acasing to abut a temperature adjustment screw. The temperatureadjustment screw has atapered outer peripheral edge, and a stop memberis held in place on the edge by engagement v with a nut which isthreaded on a projecting end of the adjustment screw.

In order to calibrate the water heater thermostat, the nut is tightenedto secure the stop, and the water temperature to which the rod and tubeare subjected is determined. The stop member is then turned by meansof adial in a first direction to snap the valve means open and then in anopposite direction to snap the valve means closed. The position of thedial when the valve means is closed is determined, and the nut isloosened so that the dial and stopmay be moved to the existing knownwater temperature. The nut is now retightened, and calibration of thethermostat is completed. Reference is made to US. Pat. No. 2,953,937 toW.F. Jackson et a]. for a more detailed description of the abovedescribed prior art calibration assembly and procedure.

Prior art space thermostats have normally utilized spring washers toprovide relative movement between a cam follower and a rotatable memberto permit calibration of the thermostat. The use of such spring wash--SUMMARY OF THE INVENTION Accordingly, it is an object of the presentinvention to construct a calibration assembly for a thermostat which hasa reduced member of components and permits simplified calibrationprocedures.

The present invention is generally summarized in a clutch spring made ofa single piece of metal formed to A further object of the presentinvention is to reduce I the number of components in thermostatcalibration assemblies.

The present invention has another object in that a cy lindrical clutchspring is used to couple a cam follower with a rotatable post in a spacethermostat.

A further object of the present invention is to use a cylindrical clutchspring to couple a temperature sensor to a rotatable post in as spacethermostat.

Another object of the present invention is to couple a movabletemperature adjusting dial with an adjustment screw in a water heaterthermostat.

Some of theadvantages of the present invention over the prior art arethat the number of calibration assembly components is reduced, assemblyprocedures are simplified, calibration procedures are simplified, andmaterial and labor costs are reduced.

- Further objects and advantages of the present invention will becomeapparent from the following description of the preferred embodimentstaken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1- is aside elevation, partiallyin section, ofa calibration assembly utilized with the space thermostatof FIG. 3.

'FIG. 6 isan exploded, perspective view of a modified calibrationassembly according to the present invention.

DESCRIPTION or THE PREFERRED EMBODIMENTS .A calibration assemblyaccording to the present invention is illustrated in FlGl l for use witha water heater thermostat. Water heater thermostatsare well know in theart and normally include a casing 10 having an inlet port, not shown,communicatingwith an outlet port 12 under the control valve means 14adapted to cooperate with a valvev seat 16 within the casing. The inletport is adapted to receive fuel from a gas source, not shown, and outletport 12 is adapted to communicate with a conduit for supplying fuel to amain burner, not shown. Valve means 14 is controlled by aconventionalsnap-acting actuating mechanism 18 including a clicker discwhich moves from an inoperative to an operative position through anover-center position with a snap action in response to an appliedoperating force. Actuating mechanism 18 is retained in an exteriorrecess formed in the rear wall of casing by means of a bowed washer 20which is press fitted into the exterior recess along with a diaphragmseal, not shown. The operating force is applied to actuating mechanism18 by an operating button 22 extending through an opening in washer 20.

Operating button 22 abuts an operating end 24 of lever 26 having anintermediate recess 28 receiving an end of a rod 30 of a rod and tubetemperature sensing assembl which is supported on casing 10 by a flangemember 31. A recess is provided at a fulcrum end 32 of lever 26 toreceive an end 34 of an extension rod 36 which is disposed within acylindrical guide 38 in casing 10 so as to be longitudinally include acopper outer tube which expands and contracts with increasing anddecreasing temperatures, respectively; and, rod 30 is normally made of amaterial having a low coefficient of thermal expansion, such as Invar,such that rod 30 moves operating end 24 of lever 26 away from operatingbutton 22 with increasing temperatures and toward operating button 22with decreasing temperatures. Lever 26 may be considered to be part ofthe temperature sensing assembly and must be properly positioned topermit accurate operation of the thermostat at predetermined settemperatures.

A calibration assembly for the control device is illustrated in FIGS. 1and 2 and includes a rotatable adjustment screw 40 having an externallythreaded portion 42 engaging a fitting 44 which threadedly engages arecess in casing 10 and is axially aligned with guide 38. Threadedportion 42 of adjustment screw 40 has an end 46 abutting extension rod36, and a small diameter shank 47 joins threaded portion 42 with acylindrical head 48 forming a clutch surface 49 and having a slot 50 inthe end thereof. A clutch spring 52 has a cylindrical sleeve-like body54 with a longitudinal edge 56. A stop portion 58 extends radially frombody 54 at a longitudinal edge 60 which is arcuately spaced from edge56, and stop portion 58 is folded upon itslef to form a leg 62 radiallyextending from longitudinal edge 60 and a radially extending leg 64spaced from leg 62 and terminating at a position spaced from thelongitudinal edge 56 of body 54. The inner diameter of the sleevelikebody of clutch 52 is slightly smaller than the outer diameter of clutchsurface 49 of adjustment screw 40 and when assembled therewithfrictionally grips the adjustment screw to turn therewith when therelative torque on the two elements is below a predetermined value. Anannular shoulder 66 is formed at the junction of shank 47 and head 48 tolimit the positioning of clutch 52 on adjustment screw 40. Clutch 52 ismounted on adjustment screw 40 is abut annular shoulder 66 by utilizinglever action to increase the inner diameter of body 54 of the clutchsuch as by inserting a screw driver in the space betweend edge 56 andleg 64 and slightly turning the screw driver.

A temperature adjusting knob 68 has a hollow center to accommodate thecalibration assembly and a recess adapted to snugly receive stop portion58 such that the calibration assembly is indexed with knob 68. lndiciamay be placed on the face of casing 10 adjacent knob 68 to correspond toindicia on the knob to permit posi tioning of the knob in accordancewith desired set temperatures.

In operation, the thermostat is mounted on a of a heater tank such thatthe rod and tube extend into the tank to sense the temperature of watertherein. The temperature assembly which valve means 14 opens iscontrolled by the initial positioning of fulcrum end 32 of lever 26under the control of adjustment screw 40. When the water temperature'within the tank drops below the predetermined temperature, end 25 oflever 26 will be moved towards the control device movable therein. Rodand tube assemblies conventionally include a copper mechanism 18 andsnap open valve means 14 to supply fuel to the burner to increase thewater temperature. Once the water obtains the predetermined temperature,lever 26'-will be moved sufficiently by withdrawal of rod 30 into thetube to permit valve means 14 to close and stop the flow of fuel to theburner.

In order to calibrate the thermostat the water temperature in the tankis determined and knob 68 is then rotated to correspond to the tankwater temperature and removed without moving clutch 52. Clutch 52 isheld stationary in any convenient manner such as by inserting a tool inthe space between legs 62 and 64' of stop portion 58, and a screw-driveris inserted in slot 50 of adjustment screw 40. Adjustment screw 40 isrotated clockwise within clutch 52 until the fulcrum end 32 of lever 26is positioned such that actuating mechanism 18 is operated to open valvemeans 14. Adjustment screw 40 is then rotated counterclockwise withinclutch 52 until valve means 14 closes. Knob 68 is then inserted over thestop portion 58 of clutch, 52 to frictionally engage the same to causeboth the knob and clutch to rotate together. Calibration is notcomplete, and a predetermined temperature at which 'it is desired tomaintain the water in the water heater may be selected by rotating knob68 which in turn rotates adjustment screw 40 by means of clutch 52 tolongitudinally nal edges 56 and permits compression gripping for theclutch and the configuration of the stop portion is advantageous forassembly and calibration. With knob 68 in place, the only force onclutch 52 is approximately 15 in. oz. and the torque differentialrequired for relative movement between adjustment screw 40 and clutch 52is 15 in. lbs. thereby providing a 16 to 1 calibration maintenancefactor.

From the above it may be seen that the clutch spring of the presentinvention is simple in construction and yet permits the construction ofextremely accurate calibration assemblies. That is, the calibrationassembly of the present invention requires essentially only a single,two-part step for calibration thereby reducing the room for error. Thecalibration assembly is further advantageous in that the number ofcomponents is reduced,

component costs are reduced calibration procedure is space thermostatincludes a base plate 70 on which is rotatably mounted an adjustmentpost 72 which is positioned by means of an annular shoulder 74 abuttingbase plate 70. A spiral bimetal 76 has an inner end 78 spot-welded topost 72 and an outer end 80 carrying a movable electrical contact 82which is adapted to cooperate with a stationary electrical contact 84having a magnet associated therewith to form a snap acting electricalswitch controlled by the space thermostat. A cam 86 is rotatably mountedon base plate 70 by means of a pin 88 and has a pointer 90adapted tomove adjacent a temperature scale 92 and a cam surface 94 upon whichrides a cam follower 96. Cam follower 96 has an apertured leg 98 whichreceives one end of a bias spring 100 mounted in tension between-leg 98and a stationary block 102 secured to mounting plate 70.

Cam follower 96 engages post 72 by means of a sleeve-like, clutch spring104 which may be formed integrally with or attached to the inner end ofcam follower 96. Clutch 104 has essentially the same configuration asclutch 52 of the embodiment of FIGS. 1 and 2 and has astop portion 106extending from the sleevelike b'ody thereof. Clutch 104 will not bedescribed in detail due to its similarity to clutch 52; however, itshould be noted that the inner surface of the body. of clutch 104 gripsa cylindrical clutch surface on post 72 adjacent annular shoulder 74.

In operation, the space thermostat is mounted such that bimetal 76senses a space temperature. Assuming the thermostat to be of a heatingvariety, when the space temperature is above a predetermined settemperature, the electrical control device or switch formed by contacts82 and 84 will present an open circuit to prevent the supply ofelectricity to an actuator which supplies fuel to a burner whenenergized. When-the space temperature drops below the set temperature,contacts 82 and 84 will close to energize the actuator and supply fuelto the burner to heat the space. Accordingly, bimetal 76 is constructedso as to rotate counterclockwise with increasing temperature andclockwise with decreasing temperature.

Initial positioning of movable contact 82 controls the temperature atwhich the electrical switch will be closed, and movable contact 82 isinitially positioned by movement of cam 86 such that cam follower 96 isaccordinglymoved to rotate post 72 and bimetal 76.

In order to calibrate the space thermostat, the existing temperature inthe space is determined, and cam 86 is moved such that pointer 90 'isaligned with the exist-- ing space temperature. Utilizing any convenienttool for engaging stop portion 106 or cam follower 96,

clutch 104 and cam follower 96 are held stationary while a screw driveris inserted in a slot in the top of post 72 and rotated counterclockwiseuntil contacts 82 and 84 are open; thereafter, post 72 is rotatedclockwise until contacts 82 and 84 snap closed. The space thermostat isnow properly calibrated and any predetermined set temperature may be.obtainedby movement of cam 86.

It may be seen that the cooperation of the clutch spring according tothe present invention with a cam follower permits the construction of acalibration assembly having the advantages previously described withrespect to the embodimentof FIGS. 1 and 2 as well as the advantages ofease of manufacture and assembly of the components.

A modification of the space thermostat calibration assembly of FIG. 3 isillustrated in FIG. 5 and identical reference numbers are used toidentify identical parts which are not described again. The primarydifference between the embodiments of FIGS. 3 and 5 is that the clutchspring is secured to theinner end 78 of bimetal 76, and cam 96 issecured to shoulder 74 of post 72 so as to rotate therewith at alltimes.

The upper portion of post 72 has a reduced diameter to form a clutchsurface for engaging a clutch spring 108. The structure of clutch 108will not be described in detail since it is essentially the same asclutch 52 of FIG. 1; however, a stop portion 110 for clutch 108 does notextend the full longitudinal length of the clutch but rather for onlyabout half the length thereof such that it extends above bimetal 76. Itwill be appreciatedthat clutch 108 may be formed integrally with thebimetal or attached thereto.

In order to calibrate a space thermostat utilizing the calibrationassembly of FIG. 5, the existing space temperature is determined and cam86 is moved such that pointer 90 is adjacent the existing spacetemperature. A screw driver or other such convenient tool is inserted inthe space between the folded legs of stop portion 110, and a screwdriver is inserted in thegroove in the topof post 72. Post 72 is thenheld stationary while clutch 108 and bimetal 76 are rotated firstcounterclockwise to open the contacts and then clockwise until thecontacts snap closed to complete calibration.

A modififed calibration assembly for use with the control device of FIG.1 is illustrated in FIG. 6 utilizing an adjustment screw 112substantially the same as adjustment screw 40 of FIG. 1. Adjustmentscrew 112 has an annular shoulder 114 to define a clutch surface withshoulder 66 and to limit movement of a clutch spring 116 in bothlongitudinal directions. Clutch spring 116 is similar to clutch 52 inthat it has a sleeve-like body 118 having spaced longitudinal edges 120and 122; however, a stop portion 124 is formed from legs 126 and 128radially extending from longitudinal edges 120 and 122, respectively.Legs 126 and 128 each have upwardly extending tabs to aid engagement ofknob 68 and bent corners to facilitate assembly of knob 68 with thecalibration assembly.

The calibration assembly of FIG. 6 is utilized in the same manner as thecalibration assembly'of FIG.'2 to calibrate the thermostat of FIG. 1. Ofcourse, clutch 116 may be slightly modified for use with the embodimentsof FIGS. 3 and 5.

Inasmuch as the present invention is subject to many variations,modifications and changes in detail, it is intended that all mattercontained in the foregoing description or shown in the accompanyingdrawing shall be interpreted as illustrative and not in a limitingsense.

edge, and said piece of metal being further formed to' define a firstleg extending outwardly from said first longitudinal edge. Y

2. The invention as recited in claim 1 wherein said piece of metal isfurther formed to define a second leg spaced from said first leg.

3. The invention as recited in claim 2 wherein said piece of metal isfolded upon itself to form said first and second legs.

4. The invention as recited in claim 3 wherein said second legterminates at a position spaced from said second longitudinal edge.

5. The invention as recited in claim 4 wherein said sleeve-like body hasa cylindrical configuration and said first and second legs are radiallydisposed relative to said sleeve-like body.

6. The invention as recited in claim 2 wherein said second leg extendsoutwardly from said second longitusleeve-like body has a cylindricalconfiguration.

' I! l t.

1. A clutch spring for use in a calibration assembly made of a singlepiece of metal, said piece of metal being formed to define a sleeve-likebody for frictionally gripping a clutch surface and having a firstlongitudinal edge arcuately spaced from a second longitudinal edge, andsaid piece of metal being further formed to define a first leg extendingoutwardly from said first longitudinal edge.
 2. The invention as recitedin claim 1 wherein said piece of metal is further formed to define asecond leg spaced from said first leg.
 3. The invention as recited inclaim 2 wherein said piece of metal is folded upon itself to form saidfirst and second legs.
 4. The invention as recited in claim 3 whereinsaid second leg terminates at a position spaced from said secondlongitudinal edge.
 5. The invention as recited in claim 4 wherein saidsleeve-like body has a cylindrical configuration and said first andsecond legs are radially disposed relative to said sleeve-like body. 6.The invention as recited in claim 2 wherein said second leg extendsoutwardly from said second longitudinal edge.
 7. The invention asrecited in claim 6 wherein said first and second legs extend radiallyfrom said first and second longitudinal edges, respectively, and each ofsaid first and second legs has an end with bent corners and a centraltab extending therefrom.
 8. The invention as recited in claim 1 whereinsaid first leg extends radially from said first longitudinal edge. 9.The invention as recited in claim 8 wherein said sleeve-like body has acylindrical configuration.